This invention relates in general to anti-lock brake systems and in particular to solenoid valve coil structure and interconnections within a removable anti-lock brake system electronic control module.
An Anti-lock Brake System (ABS) is often included as standard or optional equipment on new vehicles. When actuated, the ABS is operative to control the operation of some or all of the vehicle wheel brakes. A typical ABS includes a plurality of solenoid valves mounted within a control valve body and connected to the vehicle hydraulic brake system. Usually, a separate hydraulic source, such as a motor driven pump, is included in the ABS control valve body for reapplying hydraulic pressure to the controlled wheels during an ABS braking cycle. An ABS further includes an electronic control module which is electrically connected to the pump motor, a plurality of solenoid coils associated with the solenoid valves, and wheel speed sensors for monitoring the speed and deceleration of the controlled wheels. The electronic control module is typically mounted upon the control valve body with the assembled valve body, motor and control module forming a compact unit which is often referred to as an ABS control valve.
During vehicle operation, the ABS control module continuously receives speed signals from the wheel speed sensors. The control module monitors the speed signals for potential wheel lock-up conditions. When the vehicle brakes are applied and the control module senses an impending wheel lock-up condition, the control module is operative to actuate the pump motor and selectively operate the solenoid valves in the control valve to cyclically relieve and reapply hydraulic pressure to the controlled wheel brakes. The hydraulic pressure applied to the controlled brakes is adjusted by the operation of the solenoid valves to limit wheel slippage to a safe level while continuing to produce adequate brake torque to decelerate the vehicle as desired by the driver.
Referring now to FIG. 1, there is shown a partial sectional view of a portion of a typical ABS control valve 10. The control valve 10 includes a plurality of solenoid valves 11 (one shown) mounted in a valve body 12. Each of the solenoid valves 11 has a valve sleeve 13 which extends upwardly from the top surface of the valve body 12. Each valve sleeve 13 encloses an axially movable solenoid armature (not shown) which carries a valve ball on one end. As will be explained below, the valve sleeves 13 prevent loss of hydraulic fluid from the control valve 10 during servicing of the electronic control module.
Each valve 11 also includes a solenoid coil 15. As illustrated in FIG. 1, the coil 15 includes a winding 16 comprising a plurality of turns of fine wire wound upon a bobbin 17. The ends of the winding wire are wound onto a pair of rigid coil leads 18 which extend in an upward direction from the coil 15. An annular flux ring 20 is disposed between the coil 15 and the valve 11. A cylindrical flux casing 21 encloses the coil 15. A pair of lead apertures 22 are formed through the top surface of the casing 21. The coil leads 18 extend through the casing lead apertures 22 and through a second pair of apertures 23 formed through a Printed Circuit Board (PCB) 24. The PCB 24 has electrical traces 25 formed upon its top surface. The coil leads 18 are electrically connected to the traces 25 by a solder connection 26. Electricity is supplied through the electrical traces 25 and coil leads 18 to the coil 15. The coil 15 generates a magnetic flux field which actuates the solenoid valve 11. The flux ring 20 and flux casing 21 cooperate to provide a low reluctance return path for the magnetic flux field.
Typically, the PCB 24 carries a microprocessor and other electronic components (not shown) for controlling the ABS. As shown in FIG. 1, a removable cover 27 encloses the solenoid coils 15 and the PCB 24. The PCB 24 is usually attached to the cover 27 to form a compact integrated electronic control module 28. Because the valve sleeves 13 seal the associated solenoid valves 11, the electronic control module 28 can be removed from the control valve 10 for servicing the electronic control components without disturbing the vehicle hydraulic brake system.